FIG. 10 shows a schematic block diagram of a position control device. A reference sign 1 is a position control section, a reference sign 2 is a speed control section, a reference sign 3 is a current control section and a reference sign 4 is a mechanical property section of a rotor that is an object to be controlled (an electric motor).
The position control section 1 inputs a deviation signal between an angle command θref and an angle detection θdy which are setting inputs of the position control device, and the position control section 1 calculates an angular velocity command ωref. A difference signal between this calculated angular velocity command ωref and an angular velocity detection ωdy is determined in a subtraction section 6 and is inputted to the speed control section 2. The speed control section 2 then calculates a torque current command Tdy. The mechanical property section 4 of the rotor is controlled by this torque current command Tdy through the current control section 3. And the angular velocity detection ωdy, at this time, of the mechanical, property section 4 of the rotor is returned to the subtraction section 6 as feedback, then a difference operation (a difference calculation) between the angular velocity command ωref and the angular velocity detection ωdy is performed.
In addition, the angle detection θdy of the mechanical property section 4 is returned to a subtraction section 5 as feedback, then a difference operation (a difference calculation) between the angle command θref and the angle detection θdy is performed.
A technique that executes such position control described above is known by Patent Document 1 etc. This Patent Document 1 discloses that even in a case where parameters of resonance/antiresonance frequencyies of a mechanical system are unknown, in order to suppress vibration of the mechanical system, a vibration suppression compensator is provided, and the vibration suppression compensator inputs a deviation between a speed command determined by calculation and a speed detection signal and generates a speed command compensation signal, then the sum of this compensation signal and a speed command basic signal is set as a speed signal.
Patent Document 1: Japanese Patent Application Publication No. JP2002-325473